<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .outer{
            width: 300px;
            height: 300px;
            background-color: red;
        }
        .inner{
            width: 100px;
            height: 100px;
            background-color: forestgreen;
        }
    </style>
    <script src="jquery.3.4.1.js"></script>
</head>
<body>
    <div class="outer">
        <div class="inner"></div>
    </div>
</body>
<script>
    $('.outer').mouseout(
        function () {
            console.log('out')
        }
    )
</script>
</html>